Physiotherapists could detect changes of 12 degrees or more in single-plane movement when observing forward bending, squat or hand-over-head: A cross-sectional experiment

•Physiotherapists could visually assess change in dynamic joint movement of ≥12°.•When judging single-plane, low-speed movements.•Assessing smaller amounts of change may require other measurement tools.•Accuracy was unrelated to the activity being observed or physiotherapist attributes.•Accuracy was also unrelated the visual focus and scanning pattern used.